[freebsd] panic in bpf/unix.rs when when using FD_SET

[dignifiedquire]

While trying to get iroh working on FreeBSD, I ran into this panic during our tests

Backtrace

thread 'node::tests::test_shutdown' panicked at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/libc-0.2.153/src/unix/bsd/mod.rs:569:9:
index out of bounds: the len is 16 but the index is 16
stack backtrace:
   0: rust_begin_unwind
             at /rustc/9b00956e56009bab2aa15d7bff10916599e3d6d6/library/std/src/panicking.rs:645:5
   1: core::panicking::panic_fmt
             at /rustc/9b00956e56009bab2aa15d7bff10916599e3d6d6/library/core/src/panicking.rs:72:14
   2: core::panicking::panic_bounds_check
             at /rustc/9b00956e56009bab2aa15d7bff10916599e3d6d6/library/core/src/panicking.rs:209:5
   3: libc::unix::bsd::FD_SET
             at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/libc-0.2.153/src/unix/bsd/mod.rs:569:9
   4: netdev::bpf::unix::channel
             at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/netdev-0.25.0/src/bpf/unix.rs:199:9
   5: netdev::socket::unix::channel
             at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/netdev-0.25.0/src/socket/unix.rs:55:5
   6: netdev::gateway::unix::get_default_gateway
             at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/netdev-0.25.0/src/gateway/unix.rs:20:11
   7: netdev::interface::unix::interfaces
             at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/netdev-0.25.0/src/interface/unix.rs:96:27
   8: netdev::interface::get_interfaces
             at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/netdev-0.25.0/src/interface/mod.rs:190:5
   9: iroh_net::net::interfaces::State::new::{{closure}}
             at /root/iroh/iroh-net/src/net/interfaces.rs:225:22
  10: iroh_net::net::netmon::actor::Actor::new::{{closure}}
             at /root/iroh/iroh-net/src/net/netmon/actor.rs:83:44
  11: iroh_net::net::netmon::Monitor::new::{{closure}}
             at /root/iroh/iroh-net/src/net/netmon.rs:46:34

I haven't been able to reduce the issue, but I can reproduce reliably on the FreeBSD VM I have access to using

cargo test on this branch: n0-computer/iroh#2311

[shellrow]

Thank you for reporting.
Currently, *BSD operating systems are not officially supported. As such, we had an experimental implementation for *BSD systems. However, with the recent changes, we have switched to an approach that parses routing tables and ARP tables. This should resolve the issue you reported.